In the past various remote type radio transmitters have been developed. Among these have been transmitters located in protected locations such as bank vaults where the trip switch will send a signal either to a police patrol car or the police station to notify them of unauthorized entry. Even more recently, patch through systems have been developed whereby a mobile transceiver can be wired into a relatively complex path through device which allows a portable transceiver, through the mobile transceiver, to talk to a remote base station. These latter units are not only complex in circuitry but also, because of their complexity, are subject to increased likelihood of failure, particularly in view of a relatively rough, abusive treatment mobile transceivers in general are subjected to.
None of the prior known devices of the types enumerated have been readily adaptable to preexisting mobile transceivers without requiring extensive rewiring. Special transmit and/or receive units have also been required and certainly the cost of prior known devices have been excessive at best.
Additionally, more specific emergency communication systems have been disclosed. Among these are U.S. Pat. No. 3,290,597 entitled "Emergency Assistance Radio Signalling System", issued to George R. Denny et al; U.S. Pat. No. 3,668,526 entitled "Communication System Having Means for Causing a Distress Signal" issued to Jerome S. Raskin; U.S. Pat. No. 4,107,611 entitled "Police Protection Method and Apparatus" issued to Jack N. Holcomb, Sr.; and U.S. Pat. No. 4,162,449 entitled "Apparatus for Communicating Receipt of Transmitted Signal" issued to Bernard Bouyasounaouse.
Although the above specific system provides for means by which an emergency voice message or distress signal can be transmitted to a remote station, they all incorporate one or more of the following disadvantages: (a) the user must always report his location prior to leaving his vehicle as taught by the Holcomb and Raskin patents; (b) the system requires central station equipment to decode the emergency message as taught by the Denny and Bouyasounouse patents; (c) the system requires mental recognition of a complex audio code as taught by Raskin patent; (d) the system requires mechanical tape transport mechanisms as taught by the Denny, Holcomb and Bouyasounouse patents which mechanisms are subject to likelihood of failure, particularly in view of the relatively rough and abusive treatment mobile transceivers are continually subjected to; (e) the system causes an emergency message or distress signal to be transmitted only one time as taught by the Denny, Holcomb, Bouyasounouse patents thereby greatly increasing the likelihood of not being received by the central station or nor clearly being understood; and (f) the reliability of the emergency message or distress signal being transmitted to the central station is dependent upon the user being within range of his mobile unit as taught by the Denny, Raskin, Holcomb and Bouyasounouse patents.
The fundamental deficiency of the above referred to patents is that they do not provide a flexible, easy to use, practical and fail-safe system that is readily adaptable to pre-existing mobile transceivers without requiring rewiring thereof.